first = float(input("请输入第一个数："))
second = float(input("请输入第二个数："))
operator = input("请选择运算符：+ - * /:")
if operator =='+':
    print(first +second)
elif operator == '-':
    print(first - second)
elif operator == '*':
    print(first * second)
elif operator == '/':
    if second == 0:
       print("除数不能为零")
    else:
       print(first/second)
    
   